PCB wiring methods continue to improve, and flexible wiring techniques can reduce wire length and free up more PCB space. A fiação de PCB convencional é limitada por coordenadas de fio fixas e pela falta de fios com ângulos arbitrários. A remoção dessas limitações pode melhorar significativamente a qualidade da fiação.

Let’s start with some terminology. Definimos a fiação angular arbitrária como a fiação de fio usando segmentos angulares arbitrários e radianos. É um tipo de fiação, mas não se limita a usar apenas segmentos de linha de ângulo de 90 graus e 45 graus. Topological wiring is wire wiring that does not adhere to grids and coordinates and does not use regular or irregular grids like shape-based wiring. Vamos definir o termo fiação flexível como fiação de fio sem forma fixa que permite o recálculo da forma do fio em tempo real para atingir as seguintes possibilidades de transformação. Apenas arcos de obstáculos e suas tangentes comuns são usados ​​para formar a forma da linha. (Obstacles include pins, copper foil, forbidden areas, holes and other objects) part of the circuit of two PCB models. Os fios verde e vermelho funcionam em camadas diferentes do modelo PCB. The blue circles are the perforations. The red element is highlighted. There are also some red round pins. Use only line segments and models with an Angle of 90 degrees between them. A Figura 1B é um modelo de PCB usando arcos e ângulos arbitrários. Wiring at any Angle may seem strange, but it does have many advantages. The way it is wired is very similar to how engineers wired it by hand half a century ago. Mostra um PCB real desenvolvido em 1972 por uma empresa americana chamada Digibarn para fiação manual completa. This is a PCB board based on Intel8008 computer. A fiação angular arbitrária mostrada na Figura 2 é realmente semelhante. Why would they use arbitrary Angle wiring? Porque esse tipo de fiação tem muitas vantagens. Arbitrary Angle wiring has many advantages. First, not using the angles between line segments saves PCB space (polygons always take up more space than tangents). Traditional automatic cablers can place only three wires between adjacent components (see left and center in Figure 3). No entanto, ao fazer a fiação em qualquer ângulo, há espaço suficiente para colocar 4 fios no mesmo caminho sem violar a verificação de regra de projeto (DRC). Suponha que temos um chip de modo positivo e queremos conectar os pinos do chip a dois outros pinos. Using only 90 degrees takes up a lot of space. O uso de fiação angular arbitrária pode encurtar a distância entre o chip e outros pinos, enquanto reduz a área ocupada. In this case, the area was reduced from 30 square centimeters to 23 square centimeters. Rotating the chip at any Angle can also provide better results. In this case, the area was reduced from 23 square centimeters to 10 square centimeters. It shows a real PCB. Arbitrary Angle wiring with rotating chip function is the only wiring method for this circuit board. Esta não é apenas uma teoria, mas também uma solução prática (às vezes a única solução possível). Shows an example of a simple PCB. Topology cabler results, while automatic cabler results based on optimal shape are photos of the actual PCB. An automatic cabler based on optimal shape cannot do this because the components are rotated at arbitrary angles. Você precisa de mais área, e se você não girar os componentes, o dispositivo tem que ser maior. Layout performance would be greatly improved without parallel segments, which are often a source of crosstalk. The level of crosstalk increases linearly as the length of parallel wires increases. As the spacing between parallel wires increases, crosstalk decreases quadratic. Let’s set the level of crosstalk produced by two parallel 1mm wires spaced d to e. Se houver um ângulo entre os segmentos de fio, conforme esse ângulo aumenta, o nível de diafonia diminui. The crosstalk does not depend on the length of the wire, but only on the Angle value: where α represents the Angle between the wire segments. Consider the following three wiring methods. On the left side of Figure 8 (90 degree layout), there is the maximum wire length and the maximum emi value due to parallel line segments. In the middle of Figure 8 (45 degree layout), the wire length and emi values are reduced. On the right-hand side (at any Angle), the wire length is shortest and there are no parallel wire segments, so the interference value is negligible. So arbitrary Angle wiring helps to reduce the total wire length and significantly reduce electromagnetic interference. You also remember the effect on signal delay (conductors should not be parallel and should not be perpendicular to the PCB fiberglass). Advantages of flexible wiring Manual and automatic movement of components does not destroy the wiring in flexible wiring. O cabeador calcula automaticamente a forma ideal do fio (levando em consideração a distância de segurança necessária). Flexible cabling can therefore greatly reduce the time required to edit the topology, nicely supporting multiple recabling to meet constraints. Isso mostra um design de PCB que se move através de orifícios e pontos de ramificação. During automatic movement, wire branch points and through-holes are adjusted to the optimal position. In most computer-aided design (CAD) systems, the wiring interconnection problem is reduced to the problem of sequentially finding paths between pairs of points in a maze of pads, forbidden areas, and laid wires. Quando um caminho é encontrado, ele é fixo e se torna parte do labirinto. A desvantagem da fiação sequencial é que o resultado da fiação pode depender da ordem da fiação. Quando a qualidade topológica ainda está longe de ser perfeita, o problema de “travar” ocorre em áreas localmente pequenas. But no matter which wire you rewire, it’s not going to improve the quality of the wiring. This is a serious problem in all CAD systems using sequential optimization. This is where the bending elimination process is useful. A flexão de fio refere-se ao fenômeno de que um fio em uma rede deve contornar um objeto em outra rede para acessar um objeto. Rewiring a wire will not correct this. Um exemplo de dobra é mostrado. A lit red wire travels around a pin in the other network, and an unlit red wire connects to this pin. Os resultados do processamento automático são exibidos. In the second case (on another layer), a lighted green wire is automatically rewired by changing the wiring layer (from green to red). Eliminate wire bending by automatically optimizing wire shape (approximate arcs with line segments just to show any Angle examples without arcs). (top) original design, (bottom) after eliminating bending design. Os fios vermelhos dobrados são destacados. Em uma árvore Steiner, todas as linhas devem ser conectadas como segmentos a vértices (pontos finais e adições). No topo de cada novo vértice, três segmentos devem convergir e não mais do que três segmentos devem terminar. The Angle between the line segments that converge to the vertex shall not be less than 120 degrees. It is not very difficult to construct a Steiner with these sufficient conditional properties, but it is not necessarily minimal. Gray Steiner trees are not optimal, but black Steiner trees are. No design de comunicação prático, diferentes tipos de obstáculos devem ser considerados. Eles limitam a capacidade de construir árvores de abrangência mínima usando algoritmos e árvores de Steiner usando métodos geométricos. The obstacles are shown in gray and we recommend starting at any end vertex. If there is more than one adjacent terminating vertex, you should choose one that allows you to continue using the second vertex. It depends on the Angle. O mecanismo principal aqui é um algoritmo baseado em força que calcula as forças que atuam nos novos vértices e os move repetidamente para um ponto de equilíbrio (a magnitude e a direção das forças dependem dos fios nos pontos de ramificação adjacentes). Se o ângulo entre um par de segmentos de linha conectados a um vértice (término ou adição) for menor que 120 graus, um ponto de ramificação pode ser adicionado e, em seguida, um algoritmo mecânico pode ser usado para otimizar a posição do vértice. It’s worth noting that simply sorting all angles in descending order and adding new vertices in that order doesn’t work, and the result is worse. After adding a new node, you should check the minimum of a subnet consisting of four pins:

1. If a vertex is added to the vicinity of another newly added vertex, check for the smallest four-pin network.

2. If the four-pin network is not minimal, select a pair of “diagonal” (belonging to the quadrilateral diagonal) endpoints or virtual terminal nodes (virtual terminal nodes – wire bends).

3. The line segment that connects the endpoint (virtual endpoint) to the nearest new vertex is replaced by the line segment that connects the endpoint (virtual endpoint) to the distant new vertex.

4. Use mechanical algorithms to optimize vertex positions.

This method does not guarantee to build the smallest network, but compared with other methods, it can achieve the smallest network length without grazing. Também permite áreas onde as conexões de terminal são proibidas e o número de nós de terminal pode ser arbitrário.

Flexible wiring at any Angle has some other interesting advantages. For example, if you can automatically move many objects with the help of automatic real-time wire shape recalculation, you can create parallel serpentine lines. This cabling method makes better use of space, minimizes the number of iterations, and allows for flexible use of tolerances. If there are two serpentine lines interlaced with each other, the automatic cabler will reduce the length of one or both, depending on rule priority.

Consider the wiring of BGA components. In the traditional peripheral-to-center approach, the number of channels to the periphery is reduced by 8 with each successive layer (due to a reduction in perimeter). For example, a 28x28mm component with 784 pins requires 10 layers. Some of the layers in the diagram have escaped wiring. A Figura 16 mostra um quarto de um BGA. At the same time, when using the “center to periphery” wiring method, the number of channels required to exit to the periphery does not change from layer to layer. Isso reduzirá bastante o número de camadas. Para um tamanho de componente de 28×28 mm, 7 camadas são suficientes. Para componentes maiores, todos ganham. Figure 17 shows a quarter of the BGA. An example of BGA wiring is shown. When using the “center to periphery” cabling approach, we can complete the cabling of all networks. O cabler automático topológico de ângulo arbitrário pode fazer isso. Traditional automatic cablers cannot route this example. Shows an example of a real PCB where the engineer reduced the number of signal layers from 6 to 4 (compared to the specification). In addition, it took engineers only half a day to complete the wiring of the PCB.